1. Field of the Invention
The present invention relates to an iron core of a rotating-electric machine and, more particularly, to an iron core of a rotating-electric machine composed of laminated steel plates, and a manufacturing method for the same.
2. Description of the Related Art
FIG. 21 is a perspective view of a laminate used for an iron core of a conventional rotating-electric machine disclosed in, for example, Japanese Unexamined Patent Application Publication No. 48-9201. FIG. 22 shows a laminate of the iron core being formed by wrapping it around a cylindrical core member. FIG. 23 shows the formed iron core with its both end portions joined. A laminate 5 is fabricated by laminating a predetermined number of straight magnetic strips which are blanked out, and has a core proximal portion 5a and a plurality of teeth 5b equidistantly arranged. The laminate 5 that has been formed into a substantially hexahedral shape is wound with a winding (not shown), wrapped around a cylindrical core member 9 into a cylindrical shape, and an abutting portion 10 where both end portions thereof are abutted against each other is welded to join the end portions.
In the conventional iron core of a rotating-electric machine described above, as set forth above, a plurality of slots for accommodating the winding are formed in the magnetic strips, and the magnetic strips with the slots are stacked to form the substantially hexahedral laminate 5. The laminate 5 is wound around the cylindrical core member 9 to be shaped into a cylinder, and both end portions thereof are joined.
Such a conventional iron core 40 of a rotating-electric machine is not a cylindrical iron core from the start. Winding work can be facilitated by wrapping a winding (not shown) around the substantially hexahedral laminate 5. There is an advantage in that, since the laminated 5 is curved after installing the winding, a sectional area of a slot after curving becomes smaller than that before curving, thus allowing the winding to be disposed at a higher density.
On the other hand, in the case of the conventional iron core 40 of the rotating-electric machine having the construction described above, portions in the vicinity of both end portions are formed to have larger-radius curves than a curve of the remainder thereof, so that joining surfaces of the abutting end portions do not snugly meet, leading to unsuccessful joining when the virtually hexahedral laminate 5 is wrapped around the cylindrical core member into a cylindrical shape. More specifically, the curves near the abutting portion 10 are insufficient, and a curvature radius is uneven over an entire circumference, presenting a problem in that joining surfaces are misaligned, resulting in unsuccessful joining.
There has been another problem in that forcibly meeting the abutting portion 10 deteriorates the roundness of the iron core.
Furthermore, in the conventional iron core 40 of a rotating-electric machine having the above construction, there has been still another problem in that wavy deformation as shown in FIG. 24 occurs when the iron core 40 is cylindrically wound around the cylindrical core member 9.
There has been yet another problem in that bending rigidity at both end portions of the virtually hexahedral laminate 5 is high, and a large force is required for curving the end portions, causing a tooth portion 5b to buckle.